The growing use of cordless devices such portable electronic devices and power tools as well as the increasing need for high capacity energy storage for uses such as electrical vehicles has driven significant research into rechargeable batteries having low cost, high energy storage capacity, and high specific power. One of the most promising and rapidly growing segments of the battery market is lithium-ion based batteries. However, these batteries can have limited energy densities.
An alternative to lithium ion batteries is lithium sulfur cells, which have significantly higher theoretical energy capacities. These cells have sulfur-containing cathodes. However, since sulfur is electrically insulating, it is desirable that it be in contact with an electrically conductive additive in the electrode to enable high current rate. It is also desirable that the sulfur posse a morphology that allows for rapid charge transfer. One challenge in the development of lithium sulfur cells is that lithium sulfide species can be generated in the cathodes and during discharge. If such species are soluble in the electrolytes, they can become electrochemically unavailable (such as if they migrate through the separator and to the anode, where they could react with the anode material). This can lead to disadvantages such as capacity fade, low cycle life, high self discharge rates, etc.
Ji et al. Nature Mater. 2009, 8, 500-506 discloses a highly ordered nanostructured carbon-sulfur cathode for lithium sulfur batteries. Yuan et al. J. Power Sources 2009, 189, 1141-1146 discloses sulfur-coated multi-walled carbon nanotube composites cathodes for lithium sulfur batteries. Wang et al. Nano Lett. 2011, 11, 2644 discloses grapheme-wrapped sulfur particles as a rechargeable lithium-sulfur battery cathode material.